The present invention concerns a system for treating a physiological disorder using a drug delivery catheter; and, more particularly, relates to an implantable medical device to remotely deliver drugs, and in some instances, electrical stimulation, to a patient to regulate the heart, the vascular system, and other bodily systems.
Drug delivery therapies are often a primary component of an overall patient health plan. The successful use of many drugs is often dependent upon the manner in which the drugs are administered. Some therapies require that the drug be delivered in response to specific biofeedback indicators. Other treatments prescribe the use of predetermined drugs over a long period of time. This makes the selection of a proper drug delivery method problematic. Additionally, lack of patient compliance may render a drug therapy program ineffective. Drug delivery also becomes problematic when the drugs are too potent for systemic delivery.
For all of the foregoing reasons, it is often desirable to utilize an implantable drug delivery system. Implantable drug delivery systems are in widespread use to provide site-specific and/or sustained delivery of beneficial agents to address adverse patient conditions. Such delivery systems may include implantable infusion pumps, which typically include a pressurized drug reservoir and some form of fluid flow control.
While implantable drug delivery systems are known, such systems are generally not capable of accurately controlling the dosage of drugs delivered to the patient. This is particularly essential when dealing with drugs that can be toxic in higher concentrations. One manner of controlling drug delivery involves using electro-release techniques for controlling the delivery of a biologically-active agent or drug. The delivery process can be controlled by selectively activating the electro-release system, or by adjusting the rate of release. Several systems of this nature are described in U.S. Pat. Nos. 5,876,741 and 5,651,979 which describe a system for delivering active substances into an environment using polymer gel networks. Another drug delivery system is described in U.S. Pat. No. 5,797,898 to Santini, Jr. which discusses the use of switches provided on a microchip to control the delivery of drugs. Yet another delivery device is discussed in U.S. Pat. No. 5,368,704 which describes the use of an array of valves formed on a monolithic substrate that can be selectively activated to control the flow rate of a substance through the substrate.
None of the foregoing references describe a manner of utilizing an electro-release system within an implantable medical device such as a catheter. Therefore, what.is needed is an improved electro-release system for selectively delivering drugs alone, or in combination with, electrical stimulation to a patient to provide an optimal therapy that is not dependent on patient compliance.
The current invention provides an Implantable Medical Device (IMD) for controllably releasing a biologically-active agent such as a drug to a body. In one embodiment, the IMD includes a catheter having one or more ports, each of which is individually controlled by a respective pair of conductive members located in proximity to the port. According to the invention, a voltage potential difference generated across a respective pair of conductive members is used to control drug delivery via the respective port.
In one embodiment of the current invention, each port includes a cap member formed of a conductive material. This cap member is electrically coupled to one of the conductive members associated with the port to form an anode. The second one of the conductive members is located in proximity to the port and serves as a cathode. When the cap member is exposed to a conductive fluid such as blood, a potential difference may be generated to cause current flow from the anode to the catheter. This causes the cap member to oxidize and dissolve in the blood, which allows a biologically-active agent to be released from the catheter into the blood.
In another embodiment of the invention, each port is in proximity to a reservoir or other expandable member containing a cross-linked polymer gel of the type that expands when placed within an electrical field. Generation of a voltage potential difference in the respective conductive members associated with the port creates an electric field across the cross-linked polymer gel, causing it to expand. This expansion exerts a force on the walls of reservoir or expandable member containing the gel, which may, in turn, be used to control the release of the biologically-active agent. According to one embodiment, the expandable member is a disk having an aperture in the center that swells to a closed state upon generation of the electric field. When the aperture is in the closed state, the biologically-active agent is prevented from exiting the port. According to another embodiment, the swelling of the polymer gel exerts a force against a flexible member that forms at least a portion of the reservoir containing the polymer gel. As a result, the flexible member covers the catheter port, preventing delivery of the drug through the port. In an alternative configuration, force exerted by expansion of the polymer exerts force against a slidable member that forms at least one wall of the reservoir. As a result, slidable member exerts a force against a bolus of a drug that is located within a second reservoir of the catheter, forcing a dosage of the drug from the port.
The catheter of the current invention may include local reservoirs containing the biologically-active agents. These local reservoirs are located in proximity to a respective port. Each of the reservoirs may contain the same, or a different, biologically-active agent as compared to the other local reservoirs. Alternatively, a storage reservoir may be located remotely within an IMD coupled to the proximal end of the catheter. In this case, the remote storage reservoir may be coupled to a drug infusion pump that pumps the agent contained within the remote reservoir to one or more of the ports via-an internal lumen within the catheter body.
According to another aspect of the current invention, the IMD may include a control circuit to selectively activate one or more of the conductor pairs, thereby controlling the delivery of one or more drugs via the respective ports.
In one embodiment of the invention, the catheter may include one or more electrodes to provide electrical stimulation to the body. The control circuit of the IMD may include means to coordination this electrical stimulation with the drug delivery therapy. For example, an analgesic agent may be delivered to the body at a predetermined time prior to the delivery of cardioversion/defibrillation stimulation to thereby minimize patient discomfort associated with the electrical stimulation.
In another embodiment of the invention, the catheter may include one or more biological sensors to provide one or more biological signals to the control circuit of the IMD. The control circuit may include means to control the delivery of the electrical stimulation and/or drug delivery therapy based on the one or more biological signals provided by the biological sensors.
According to yet another aspect of the invention, the ports of the catheter may be of varying sizes. By selectively allowing drug delivery to be performed via a predetermined combination of these ports, a precise drug dosage may be released to the body.
Other aspects of the invention will be apparent to those skilled in the art from the following description and the accompanying drawings.